Major patches drop roughly every three months, with minor patches releasing three weeks
The .x to .x1 patches are usually 2 or 2.5 (for the .0 to .01) weeks apart.

.x to .x5 is almost always 6 weeks, and then 6-10 weeks for the next major patch.

.35 to .4 in stormblood was over 2.5 months, made worse by the only content in-between those being the worst (by far) eureka step.

https://ffxiv.gamerescape.com/wiki/C...hes#Stormblood